Pipeline construction

ABSTRACT

In order to insulate a pipeline from the earth in which it is buried, the pipe is surrounded by a mass of dry earth, sand and/or gravel and a water-impermeable membrane.

United States Patent Keene 51 July 11,1972

[54 I PIPELINE CONSTRUCTION Wllllnm A. Keene. Bartlesville Okla.

[73] Assignee: Phllllpe Petroleum Company [22] Filed: Feb. 28, I971 [21]Appl. No.: "0,451

I72] Inventor:

[52] US. Cl ..6l/72.l, 138/105 Field of Search ..6l/72. l 72.2, 72.5,72.6, 6l/72.7; l38/l05; 52/169, 743, 404; l38/IO6 [56] References CitedUNITED STATES PATENTS 2,901,775 9/1959 Golf l38/l05 X 2.007.969 7/1935Grodsky I 2,360,067 10/1945 Mcbeish l38/l05 Primary Examiner-.laoobShapiro Attorney-Young and Quigg ABSTRACT In order to insulate apipeline from the earth in which it is buried, the pipe is surrounded bya mass of dry earth, sand and/or gravel and a water-impermeablemembrane.

10 Clalrm, 3 Drawingfiguns WY A X PATENTEnJuL 1 1 19. 2

FIG. 2

INVENTOR.

W. A. KEENE ATTORNEYS PIPELINE CONSTRUCTION Considerable difiiculty isoften encountered in constructing pipelines which are to convey fluidsat temperatures appreciably difierent from the temperature of the earthin which the pipeline is buried. This is particularly true when apipeline is to be buried in regions of permafrost. in order to pumpcrude oil through pipelines in arctic regions, it is necessary to heatthe oil so that the viscosity is sufficiently low to permit the oil tobe pumped. Unless the pipeline is well insulated, excessive heat losswill occur. In addition to increasing the viscosity of the oil, the heatloss may tend to melt the surrounding permafrost, which can cause ashifting and pomible rupture of the pipeline. While various types ofinsulating materials are known, the costs of most such materials areusually quite high for extensive pipeline use. In accordance with thisinvention, a low cost method is provided for constructing pipelineswhich are adapted to be used in transporting materials at temperaturesdiflerent from the temperature of the surrounding earth formation. Thisis accomplished by first digging a trench into which the pipeline is tobe buried. The trench is lined with a water-impermeable membrane, suchas a sheet of heavy thermoplastic material. The trench is then filledwith dry earth, sand and/or gravel and the pipeline is buried in thefill material. The water-impermeable liner is sealed over the top of thefilled trench to prevent water from permeating the dry fill material.The dry earth, sand and/or gravel employed to fill the trench canadvantageously be obtained by drying the material initially removed fromthe trench.

IN THE ACCOMPANYING DRAWING FIG. 1 is a schematic cross-sectional viewof a pipeline constructed in accordance with this invention.

FIG. 2 illustrates a water-impermeable barrier which can be secured tothe pipe at spaced locations.

FIG. 3 is a schematic illustration of a second embodiment of a pipelineconstructed in accordance with this invention.

Referring now to the drawing in detail and to FIG. 1 in particular,there is shown a cross-section of earth which contains permafrost. Thefirst step of the method of this invention involves digging a trench inthe earth along the route of the pipeline. A water-impermeable liner 11is then positioned in the trench so as to extend longitudinally alongthe trench. This liner can advantageously be formed of a flexible sheetof heavy gage thermoplastic material, such as polyethylene. However,other types of water-impermeable material can be employed, such asasphalt impregnated woven or nonwoven sheet materials, for example. Amulti-layer sheet may be advantageous in certain operations. The linedtrench is then filled with dry earth, sand and/or gravel to support apipe 13 in the central region of the trench. [n this operation, thetrench can be filled approximately half full with the dry material, andthe pipe can then be positioned in the trench. The remainder of thetrench is then filled with additional dry material to enclose the pipe.The edges of liner 1 l are sealed together across the top of the filledtrench. This can be accomplished by a heat sealing step or by the use ofa suitable adhesive, depending on the nature of the material used as theliner. A fill material 14 can then be disposed over the top of the linerto prevent the liner from subsequently being damaged.

The dry earth, sand and/or gravel utilized to fill the trench can beobtained by heating the material initially removed from the trench toremove moisture contained therein. This can be accomplished by the useof a portable kiln which can be moved along as the pipeline is beingconstructed. lf the material initially removed from the trench containsany appreciable amount of organic material, the heating step can includethe introduction of air and the use of sufficiently high temperatures toburn this organic material. The resulting dried material which isreturned to the trench provides an eflicient heat insulator, and linerll prevents subsequent moisture invasion. If the earth formationcontains an appreciable amount of water, it may be necessary to utilizeadditional fill obtained from another location to replace the lostvolume of the water.

It is desirable to provide vertical water-impermeable barriers at spacedlocations along the pipe so that a series of individual compartments areformed. This confines water invasion in the event that a section ofliner 11 is ruptured. The vertical barriers can be formed by the use ofsheets of film 15 which are secured to pipe 13 at spaced locations. Asillustrated in FIG. 2, such a membrane 15 is provided with a centralopening which can contain a collar 16 which is secured to the pipe bythe use of an adhesive or by fusing the plastic to the pipe. Sheet 15 isof sufficient size to extend across the cross-section of the trench. Theedges of sheet 15 are fastened to liner 1 l in fluid-tight engagement.

Ifdesired, additional insulating material can be employed inconstructing the pipeline of this invention. As illustrated in FIG. 3,an outer layer of conventional heat insulating material 16, such aspolyurethane foam, for example, can line the trench, and pipe 13 can besurrounded by a sheath of heat insulating material 17. [f the insulatingmaterial selected for this purpose is water-impermeable, line 11 is notrequired. Otherwise, the liner can be employed in the same manner asillustrated in FIG. 1.

While this invention has been described in conjunction with theconstruction of oil pipelines in permafrost, the invention is applicableto any type of pipeline wherein the temperature of the fluid beingtransported diflers substantially from the temperature of thesurrounding earth formation. Such a pipeline can be employed to conveyhigh temperature materials, such as molten sulfur, or low temperaturematerials, such as liquefied natural gas, for example. The dry earth,sand and/or gravel provides a low cost, efficient insulator. The size ofthe trench will depend on the size of the pipeline and the temperaturedifferences to be encountered. A trench some ten feet square incross-section can be employed if an oil pipeline is to be constructed inpermafrost, for example. When a pipeline is constructed in permafrost inaccordance with this invention, the dry material also serves as a spreadfoundation for the pipe. This is particularly true when grave] isemployed to enclose the pipe. Such a foundation is quite effective inareas of permafrost.

While the invention has been described in conjunction with presentlypreferred embodiments, it should be evident that it is not limitedthereto.

What is claimed is:

1. The method of laying a pipeline which comprises excavating a trenchto receive the pipe; lining the trench with a water-impermeable liner;drying a quantity of earth, sand and/or gravel to remove moisturetherefrom; positioning pipe and the thus dried earth, sand and/or gravelwithin the lined trench so that the pipe extends longitudinally of thetrench and is surrounded by the dry earth, sand and/or gravel; andsealing the edges of the liner to form a water-impermeable barrieraround the pipe and dry earth, sand and/or gravel.

2. The method of claim 1 wherein the material removed during theexcavation step is dried to form the dry material employed to surroundthe pipe in the trench.

3. The method of claim 2 wherein the material is dried at an elevatedtemperature in the presence of oxygen to burn or ganic materialcontained therein.

4. The method of claim 1, further comprising positioning a series ofwater-impermeable second barriers in the trench in spaced relationshipwith one another, each of said second barriers extending from the pipeto the surrounding liner; and sealing said second barriers to said pipeand the surrounding liner to form a series of water-impermeablecompartments.

5. A pipeline comprising a pipe positioned in the earth; a mass of dryearth, sand and/or gravel free of organic material surrounding saidpipe; and a water-impermeable membrane enclosing said pipe andsurrounding dry earth, sand and/or gravel.

6. The pipeline 0s claim 5, further comprising a series of secondwater-impermeable membranes positioned in spaced relationship with oneanother, each of said second membranes being sealed to and extendingbetween said pipe and said firstmentioned membrane.

10. The method of laying a pipeline which comprises excavating a trenchto receive the pipe; lining the trench with a water-impermeable liner;positioning pipe and dry earth, sand and/or gravel which is free oforganic material within the lined trench so that the pipe extendslongitudinally of the trench and is surrounded by the earth, sand and/orgravel; and sealing the edges of the liner to form a water-impermeablebarrier around the earth, sand and/or gravel.

t i i l i UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Dated: y11, 1972 atent Noo 3,675,152 William A. Keene -identified patent andthat saic It is certified that error appears in the above etters Patentare hereby corrected as shown below:

Cover page, first column, No. [221 should read as follows:

-- [22] Filed Jan. 28, 1971 Column 2, line 71, change "05 to ofSignedend sealed this 26th day of December 1972.

EDWARD ILFLEJJCI'IFRJR. ROBERT GOT'ISCHALK Attesfilng OfficerCommissioner of Patents

1. The method of laying a pipeline which comprises excavating a trenchto receive the pipe; lining the trench with a waterimpermeable liner;drying a quantity of earth, sand and/or gravel to remove moisturetherefrom; positioning pipe and the thus dried earth, sand and/or gravelwithin the lined trench so that the pipe extends longitudinally of thetrench and is surrounded by the dry earth, sand and/or gravel; andsealing the edges of the liner to form a water-impermeable barrieraround the pipe and dry earth, sand and/or gravel.
 2. The method ofclaim 1 wherein the material removed duRing the excavation step is driedto form the dry material employed to surround the pipe in the trench. 3.The method of claim 2 wherein the material is dried at an elevatedtemperature in the presence of oxygen to burn organic material containedtherein.
 4. The method of claim 1, further comprising positioning aseries of water-impermeable second barriers in the trench in spacedrelationship with one another, each of said second barriers extendingfrom the pipe to the surrounding liner; and sealing said second barriersto said pipe and the surrounding liner to form a series ofwater-impermeable compartments.
 5. A pipeline comprising a pipepositioned in the earth; a mass of dry earth, sand and/or gravel free oforganic material surrounding said pipe; and a water-impermeable membraneenclosing said pipe and surrounding dry earth, sand and/or gravel. 6.The pipeline of claim 5, further comprising a series of secondwater-impermeable membranes positioned in spaced relationship with oneanother, each of said second membranes being sealed to and extendingbetween said pipe and said first-mentioned membrane.
 7. The pipeline ofclaim 5, further comprising a sheath of heat insulating materialsurrounding said pipe and being positioned between said pipe and saiddry earth, sand and/or gravel.
 8. The pipeline of claim 5, furthercomprising a mass of heat insulating material positioned between saiddry earth, sand and/or gravel and said membrane.
 9. The method of claim1 wherein the earth, sand and/or gravel is dried at an elevatedtemperature in the presence of oxygen to burn organic material containedtherein.
 10. The method of laying a pipeline which comprises excavatinga trench to receive the pipe; lining the trench with a water-impermeableliner; positioning pipe and dry earth, sand and/or gravel which is freeof organic material within the lined trench so that the pipe extendslongitudinally of the trench and is surrounded by the earth, sand and/orgravel; and sealing the edges of the liner to form a water-impermeablebarrier around the earth, sand and/or gravel.